The invention relates to a blanking platen of a press for shaping sheets of paper or cardboard, comprising a bottom beam receiving a support plate on which a metal cutting sheet can be placed, the support plate comprising means for adjusting its position in a horizontal plane and means for fixing the support plate.
For each run, presses for shaping sheets of paper, solid fibreboard or corrugated cardboard use a specific set of shaping tools for a given job. A typical set of tools comprises:
a make-ready sheet,
a support member,
a top ejection member,
a bottom ejection board,
a top blank-separating tool,
a bottom blank-separating tool, and
if required, a front waste separator.
The set of tools must be disposed extremely accurately in the various stations of the press at the beginning of each job. In the case of short runs in particular, the productivity of the unit depends closely on the speed with which the tools are positioned and adjusted.
In a blanking platen of the kind defined in the preamble, the metal cutting plate can be used as a support for corresponding scoring parts co-operating with scoring rules mounted on the support member. In this case the cutting plate may be considered as an additional shaping tool. The co-operating parts opposite the scoring rules must be positioned extremely accurately and this operation needs to be optimised, like the adjustment of the other tools.
The support plates in existing presses are often provided with a device for micrometric adjustment of the longitudinal position of the plate with respect to the beam. The cutting plate is screwed to the support plate by four screws at the four corners.
The screw holes have an oblong clearance or configuration and enable the position of the cutting plate on the support plate to be adjusted by about 1 mm, thus enabling the position of the grooves of the corresponding scoring parts opposite the scoring rules to be accurately adjusted in the longitudinal and transverse directions.
The terms xe2x80x9clongitudinalxe2x80x9d and xe2x80x9ctransversexe2x80x9d referring to movement and xe2x80x9cfrontxe2x80x9d, xe2x80x9crearxe2x80x9d and xe2x80x9clateralxe2x80x9d referring to a side of the support plate or of the cutting sheet are used here with reference to the direction of advance of the sheets in the machine.
However this adjustment takes a long time, since during each movement of the cutting plate during adjustment, it is necessary to remove the support plate completely from the cutting station, loosen the four screws with a screwdriver, slide the cutting plate a short distance, then tighten the four screws and return the support plate to the station in order to make a positioning test. It is generally necessary to perform these operations several times.
The object of the invention is to enable the cutting plate to be fixed and micrometrically adjusted in position much more quickly than the operation described hereinbefore.
To this end, in the case of a platen of the kind defined in the preamble, the support plate on a first side thereof comprises at least one moving stirrup, the moving stirrup being adapted to take up a clamping position where it prevents the cutting plate from sliding on the support plate and an inoperative position where it enables the cutting plate to slide on the support plate, whereas on the side opposite the first side and on an adjacent side, the support plate comprises at least one respective fixed stirrup disposed so that edge portions of the cutting plate can be slid into the fixed stirrup and be gripped under the moving stirrup in the clamping position.
When the moving stirrup is placed in the inoperative position, the cutting plate can be moved by sliding on the support plate. The cutting plate can also be moved by at least 1 mm in any direction while remaining engaged in the fixed stirrups, which is sufficient for precise adjustment of the position thereof. The operations of clamping and releasing the support plate from the moving stirrup are much quicker than tightening and loosening four screws. There is no need for the support plate to be completely taken out and returned several times to the cutting station.
The fixed stirrups can be rules having a protruding upper lip on which the cutting plate slides.
Preferably the support plate has two moving stirrups on the side near the operator, i.e. the side usually accessible by the operators. The side opposite the operator comprises two or more fixed stirrups. Likewise the rear of the support plate can comprise two or more fixed stirrups in the form of rules. The front of the support plate can carry one or more abutments.
The moving stirrup or stirrups can be mounted on a moving push rod which can be manually actuated so as to counteract the force of a return spring and raise and rotate the moving stirrup by a fraction of a revolution, moving from the inoperative position to the clamping position.
This operation can be carried out via a milled button. The cutting plate can be clamped by additional rotation of the milled button. It is thus unnecessary to use manual tools such as screwdrivers or spanners.
On its bottom surface, the support plate can be formed with a set of grooves and through-holes, connected to an air suction device. The cutting plate is thus pressed and held against the support plate by partial evacuation.
Preferably the moving stirrups are retracted into recesses in the support plate when they are rotated into the inoperative position. This enables the cutting plate to be positioned and removed by sliding it on the support plate.
The system for micrometric adjustment of the support plate, on each lateral edge of the plate, can comprise means for micrometric adjustment of its longitudinal position. The means can comprise a milled knob mounted in a block secured to the respective side edge, acting on a fixed abutment of the machine via a lug movable in the longitudinal direction and thus controlling the longitudinal position of the support plate. In a preferred embodiment, the lateral edge of the support plate near the operator can bear a second milled knob acting on a fixed abutment of the platen via a lug which moves transversely, adjusting the transverse position of the support plate, also starting from the cutting plate without unclamping it.
Other properties and advantages of the device according to the invention will be clear to the skilled man from the following description of a preferred embodiment in connection with the drawings, in which: